Hitherto, for example, in a device including a rotating shaft that transmits torque, such as a flywheel energy storage system capable of converting rotational energy into electrical energy or converting electrical energy into rotational energy, so-called vacuum separation is performed in which the atmosphere and a vacuum space are separated by using a magnetic fluid sealing device. As described above, by assembling the magnetic fluid sealing device to the rotating shaft that rotates at a high speed, the atmosphere and the vacuum space can be separated from each other.
On the other hand, the rotating shaft described above rotates at a high speed. Therefore, frictional heat is generated in the magnetic fluid sealing device due to high-speed rotation of the rotating shaft, and it is thus necessary to dissipate the frictional heat. For the purpose of dissipating the frictional heat generated in the magnetic fluid sealing device due to the high-speed rotation of the rotating shaft, a configuration in which heat dissipating fins are provided in the housing of a device to dissipate frictional heat to the atmosphere is proposed (for example, refer to Patent Documents 1 and 2).
In addition, in order to dissipate the frictional heat generated in the magnetic fluid sealing device described above, it is proposed that a cooling mechanism or a heat insulating mechanism is provided in the rotating shaft (for example, refer to Patent Documents 3 and 4).
In addition, in order to dissipate frictional heat generated in the rotating shaft during high-speed rotation, it is proposed that the rotating shaft is formed in a hollow shape and fins are provided on a part of thereof (for example, refer to Patent Document 5). In addition, a technique in which a core made of aluminum having high thermal conductivity is provided on a part of the rotating shaft to act as a part of a thermal shunt between both end portions of the rotating shaft thereby achieving heat dissipation is also proposed (for example, refer to Patent Document 6).